This invention relates in general to dampers for articulated helicopter rotors and in particular to a unique damper for lead lag motion of the blades.
In modern helicopters, the rotor blades are articulated to provide motion for blade pitch, flap and lead lag motion. Dampers are required in this lead lag motion in order to prevent air and/or ground resonance problems. The conventional means for providing this damping is to attach a hydraulic or elastomeric damper between each blade root end and the hub rotor hub of the helicopter. In a four-bladed helicopter rotor for example this would require four separate dampers and their accompanying attachment mechanisms to provide lead-lag damping. These dampers and their attachment hardware add substantially to the maintenance costs and weight of the helicopter and generally increase the rotor head height which is also an undesirable characteristic since rotor height contributes substantially to the aircraft's aerodynamic drag
In conventional articulated helicopters, a separate hinge is provided for each of the three motions of the blade. Thus a four bladed helicopter would require twelve separate hinges as well as the four individual lead lag dampers. One method of reducing complications in the rotor hub is to provide a spherical elastomeric bearings for attaching the blade to the rotor head. Such bearings eliminate the individual hinges by providing a spherical rotating member which provides coincident hinge points for all three blade motions. However, lead lag damping is still required and previously has been conventionally provided by individual hydraulic or elastomeric dampers.
The present invention provides a helicopter hub utilizing spherical elastomeric bearings to support the blades and providing coincident hinges and additionally, providing a single lead lag damper assembly within the hollow hub of the rotor head which provides elastomeric lead-lag damping for all blades simultaneously and can be configured for either blade-to-ground damping or blade-to- blade damping or combinations thereof as required.